The present invention relates to lenses having optical parameters that are adjustable in-situ. More particularly, the invention has applications in IOLs for in-capsule implantation for cataract patients, and in contact lenses, wherein an external energy source is applied to the lens to control movement of fluid media within interior cells of the lens, thereby altering the lens curvature to correct aberrations.
Cataracts are a major cause of blindness in the world and the most prevalent ocular disease. Visual disability from cataracts accounts for more than 8 million physician office visits per year. When the disability from cataracts affects or alters an individual""s activities of daily living, surgical lens removal with intraocular lens (IOL) implantation is the preferred method of treating the functional limitations. In the United States, about 2.5 million cataract surgical procedures are performed annually, making it the most common surgery for Americans over the age of 65. About 97 percent of cataract surgery patients receive intraocular lens implants, with the annual costs for cataract surgery and associated care in the United States being upwards of $4 billion.
A cataract is any opacity of a patient""s lens, whether it is a localized opacity or a diffuse general loss of transparency. To be clinically significant, however, the cataract must cause a significant reduction in visual acuity or a functional impairment. A cataract occurs as a result of aging or secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, or radiation. Age related cataract conditions are the most common.
In treating a cataract, the surgeon removes the crystalline lens matrix from the lens capsule and replaces it with an intraocular lens (xe2x80x9cIOLxe2x80x9d) implant. The typical IOL provides a selected focal length that allows the patient to have fairly good distance vision. Since the lens can no longer accommodate, the patient typically needs glasses for reading. The surgeon selects the power of the IOL based on analysis of refractive characteristics of the patient""s eye prior to the surgery. However, in a significant number of cases, after the patient""s eye has healed from the cataract surgery, there is a refractive error that could not be predicted. It is quite common for residual errors after IOL implantation to occur, and in fact, such errors may occur in the vast majority of IOL patients. This error reportedly averages approximately 0.6 diopters, with a +/xe2x88x920.5 standard deviation. Thus, many patients experience an error of over 1.0 diopter.
Various types of methods and apparatus have been proposed for altering the corrective power of an ophthalmic lens in-situ. For example, U.S. Pat. No. 6,450,642 to Jethmalani et al. describes a lens that is capable of post-fabrication power adjustment. Specifically, a partially polymerized polymer lens matrix is described that is capable of stimulus-induced further polymerization to permanently alter the lens in a selected shape.
U.S. Pat. No. 5,443,506 to Garabet describes a fluid-filled lens wherein the focusing power may be altered by changing the index of refraction of fluid carried within a central optic portion. U.S. Pat. No. 5,066,301 to Wiley describes an IOL having a fluid-filled or gel-filled lens that carries a plurality of light-reflective particles, wherein the orientation of the particles is controlled by an electromagnetic field to thereby alter the spherical power of the lens. In another similar approach, U.S. Pat. No. 4,787,903 to Grendahl discloses a fresnel-type IOL with an overlying layer of a liquid crystalline composition that has a variable index of refraction depending upon its stimulation by electrical or light energy to provide a post-implant adjustability.
U.S. Pat. No. 4,816,031 to Pfoff discloses an IOL with a hard PMMA lens separated by a single chamber from a flexible thin lens layer. The lens assembly is adjusted by microfluid pumps that vary a volume of fluid between the PMMA lens portion and the thin layer portion. U.S. Pat. No. 5,288,293 to O""Donnell discloses an intraocular lens comprising a plurality of layers of materials that respond to the application of laser energy to form microfenestrations that alter the anterior lens curvature.
Although previously known workers in the field of in-situ adjustable lenses have made some progress, the relative complexity of the methods and apparatus developed to date have prevented widespread commercialization of such devices. Moreover, previously known methods and apparatus have been directed to in-situ modifications that attempt to alter the lens axial position within the eye or overall curvature of the lens. However, such gross modifications to lens position or curvature are limited by materials and space constraints.
In view of the foregoing, it would be desirable to develop in-situ adjustable lenses that overcome the drawbacks of previously known devices. It would therefore be desirable to provide apparatus and methods that enable localized modification of the surface of a lens to correct errors, such as defocus error. This may be commonly thought of as moving the focus of the IOL system to the retina, and may be effected by actual axial motion and/or modification of the surface of the IOL, e.g., by changing the radius of curvature of one or more of the surfaces of the IOL.
In addition to modifying the placement of the focal point at the retina, it would be desirable to provide methods and apparatus that permit in-situ localized correction of other aberration properties of the eye, for example astigmatism of the eye, which may be associated with the cornea, or to correct higher order aberrations to improve visual acuity.
It also would be advantageous to provide methods and apparatus for manipulating the surface of an IOL on a localized basis after the IOL has been implanted and the access incision has healed. In order to provide such in-situ modification of the IOL surface, it would be desirable to provide an IOL configured to be modified by application of energy from a remote source, such as a laser, radio-frequency energy or ultrasonically.
It still further would be desirable to provide methods and apparatus for manipulating the surface of a lens in-situ, wherein the application of energy from an external source is performed in cooperation with a wavefront sensor system, so as to permit optimization of localized correction of the lens.
In view of the foregoing, it is an object of the present invention to provide apparatus and methods that enable localized in-situ modification of the surface of a lens to correct errors, such as defocus error, astigmatism and higher order aberrations.
It is also an object of this invention to provide apparatus and methods that enable localized in-situ modification of the surface of a lens to not only restore loss of sight due to cataracts, but which actually improve visual acuity.
It is another object of the present invention to provide methods and apparatus for manipulating the surface of an IOL on a localized basis after the IOL has been implanted and the access incision has healed.
It is a further object of the present invention to provide methods and apparatus for in-situ localized modification of the lens surface by application of energy from a remote source, such as a laser, radio-frequency energy, chemically or ultrasonically.
It is another object of this invention to provide methods and apparatus for manipulating the surface of a lens in-situ wherein the application of energy from an external source is performed in cooperation with a wavefront sensor system, so as to permit optimization of localized correction of the lens.
These and other objects of the present invention are accomplished by providing a lens including an optic element comprising resilient, locally-deformable anterior and posterior polymer elements sandwiched against an array of deformable cells. The array of deformable cells is index-matched to the anterior and posterior elements and may be surrounded by a fluid that also is index-matched with the polymer of the lens. Each of the deformable cells in turn defines a secondary fluid-filled chamber having an adjustable interior fluid volume, so that changes in the volume of the deformable cells result in corresponding localized deformation of surfaces of the anterior and/or posterior elements.
The deformable cells generally are adapted to be moved controllably between a retracted position and an axially-extended position to engage and controllably deform the anterior and/or posterior lens element upon the application of energy from an external energy source, such as a laser source. The number of cells may vary from as few as one to more than 250, and preferably are individually controllable using an external power source. The lens of the invention thus allows for a post-implant power adjustment of an IOL with an inexpensive low power laser source.
In accordance with the present invention, a selected number of deformable cells, or even a single cell, may be adjusted to alter a local region of the anterior and/or posterior lens surface, for example to correct an astigmatism or higher order aberration. Alternatively, the deformable cells within a region may be moved controllably to an axially extended position to alter the anterior and/or posterior lens surface globally to correct the sphere of the lens.
In accordance with one aspect of the present invention, an exemplary lens provides paired fluid inflow and outflow channels that communicate with each fluid-filled cell. Further, a non-optic portion of the lens carries a reservoir system that is coupled to the inflow and outflow channels by flow control mechanisms, such as one-way valves or sacrificial plugs, that allow flows of fluid to and/or from the reservoir system under the application of energy from an external source, such as from a laser source. Depending upon the specific flow control mechanisms employed in the lens, power adjustment of the lens may be performed on a one-time basis or may be periodically repeated post-implant over the lifetime of the patient.
In accordance with another aspect of this invention, the external source that targets and addresses the flow control mechanisms within the IOL may be under the control of a wavefront sensor system, thus allowing for intraoperative lens power calculations while adjusting the lens power.
According to yet another aspect of this invention, a contact lens constructed as described above may be adjusted in-situ in a patient""s eye using an external energy source and a wavefront sensor system to optimize visual acuity achievable with the lens.
Methods of using and adjusting the lens of the present invention also are provided.